/*
 * Copyright (C) 2009-2012 Free Software Foundation, Inc.
 *
 * Author: Steve Dispensa (<dispensa@phonefactor.com>)
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

#include <gnutls_int.h>
#include <ext/safe_renegotiation.h>
#include <gnutls_errors.h>


static int _gnutls_sr_recv_params (gnutls_session_t state,
                                   const uint8_t * data, size_t data_size);
static int _gnutls_sr_send_params (gnutls_session_t state, gnutls_buffer_st*);
static void _gnutls_sr_deinit_data (extension_priv_data_t priv);

extension_entry_st ext_mod_sr = {
  .name = "SAFE RENEGOTIATION",
  .type = GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
  .parse_type = GNUTLS_EXT_MANDATORY,

  .recv_func = _gnutls_sr_recv_params,
  .send_func = _gnutls_sr_send_params,
  .pack_func = NULL,
  .unpack_func = NULL,
  .deinit_func = _gnutls_sr_deinit_data,
};

int
_gnutls_ext_sr_finished (gnutls_session_t session, void *vdata,
                         size_t vdata_size, int dir)
{
  int ret;
  sr_ext_st *priv;
  extension_priv_data_t epriv;

  if (session->internals.priorities.sr == SR_DISABLED)
    {
      return 0;
    }

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }
  priv = epriv.ptr;

  /* Save data for safe renegotiation. 
   */
  if (vdata_size > MAX_VERIFY_DATA_SIZE)
    {
      gnutls_assert ();
      return GNUTLS_E_INTERNAL_ERROR;
    }

  if ((session->security_parameters.entity == GNUTLS_CLIENT && dir == 0) ||
      (session->security_parameters.entity == GNUTLS_SERVER && dir == 1))
    {
      priv->client_verify_data_len = vdata_size;
      memcpy (priv->client_verify_data, vdata, vdata_size);
    }
  else
    {
      priv->server_verify_data_len = vdata_size;
      memcpy (priv->server_verify_data, vdata, vdata_size);
    }

  return 0;
}

int
_gnutls_ext_sr_verify (gnutls_session_t session)
{
  int ret;
  sr_ext_st *priv = NULL;
  extension_priv_data_t epriv;

  if (session->internals.priorities.sr == SR_DISABLED)
    {
      gnutls_assert ();
      return 0;
    }

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret >= 0)
    priv = epriv.ptr;

  /* Safe renegotiation */

  if (priv && priv->safe_renegotiation_received)
    {
      if ((priv->ri_extension_data_len < priv->client_verify_data_len) ||
          (memcmp (priv->ri_extension_data,
                   priv->client_verify_data, priv->client_verify_data_len)))
        {
          gnutls_assert ();
          _gnutls_handshake_log ("HSK[%p]: Safe renegotiation failed [1]\n",
                                 session);
          return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
        }

      if (session->security_parameters.entity == GNUTLS_CLIENT)
        {
          if ((priv->ri_extension_data_len !=
               priv->client_verify_data_len + priv->server_verify_data_len) ||
              memcmp (priv->ri_extension_data + priv->client_verify_data_len,
                      priv->server_verify_data,
                      priv->server_verify_data_len) != 0)
            {
              gnutls_assert ();
              _gnutls_handshake_log
                ("HSK[%p]: Safe renegotiation failed [2]\n", session);
              return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
            }
        }
      else                      /* Make sure there are 0 extra bytes */
        {
          if (priv->ri_extension_data_len != priv->client_verify_data_len)
            {
              gnutls_assert ();
              _gnutls_handshake_log
                ("HSK[%p]: Safe renegotiation failed [3]\n", session);
              return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
            }
        }

      _gnutls_handshake_log ("HSK[%p]: Safe renegotiation succeeded\n",
                             session);
    }
  else                          /* safe renegotiation not received... */
    {
      if (priv && priv->connection_using_safe_renegotiation)
        {
          gnutls_assert ();
          _gnutls_handshake_log
            ("HSK[%p]: Peer previously asked for safe renegotiation\n",
             session);
          return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
        }

      /* Clients can't tell if it's an initial negotiation */
      if (session->internals.initial_negotiation_completed)
        {
          if (session->internals.priorities.sr < SR_PARTIAL)
            {
              _gnutls_handshake_log
                ("HSK[%p]: Allowing unsafe (re)negotiation\n", session);
            }
          else
            {
              gnutls_assert ();
              _gnutls_handshake_log
                ("HSK[%p]: Denying unsafe (re)negotiation\n", session);
              return GNUTLS_E_UNSAFE_RENEGOTIATION_DENIED;
            }
        }
      else
        {
          if (session->internals.priorities.sr < SR_SAFE)
            {
              _gnutls_handshake_log
                ("HSK[%p]: Allowing unsafe initial negotiation\n", session);
            }
          else
            {
              gnutls_assert ();
              _gnutls_handshake_log
                ("HSK[%p]: Denying unsafe initial negotiation\n", session);
              return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
            }
        }
    }

  return 0;
}

/* if a server received the special ciphersuite.
 */
int
_gnutls_ext_sr_recv_cs (gnutls_session_t session)
{
  int ret, set = 0;
  sr_ext_st *priv;
  extension_priv_data_t epriv;

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0)
    {
      set = 1;
    }
  else if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  if (set != 0)
    {
      priv = gnutls_calloc (1, sizeof (*priv));
      if (priv == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_MEMORY_ERROR;
        }
      epriv.ptr = priv;
    }
  else
    priv = epriv.ptr;

  priv->safe_renegotiation_received = 1;
  priv->connection_using_safe_renegotiation = 1;

  if (set != 0)
    _gnutls_ext_set_session_data (session,
                                  GNUTLS_EXTENSION_SAFE_RENEGOTIATION, epriv);

  return 0;
}

int
_gnutls_ext_sr_send_cs (gnutls_session_t session)
{
  int ret, set = 0;
  sr_ext_st *priv;
  extension_priv_data_t epriv;

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0)
    {
      set = 1;
    }
  else if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  if (set != 0)
    {
      priv = gnutls_calloc (1, sizeof (*priv));
      if (priv == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_MEMORY_ERROR;
        }
      epriv.ptr = priv;
    }
  else
    priv = epriv.ptr;

  if (set != 0)
    _gnutls_ext_set_session_data (session,
                                  GNUTLS_EXTENSION_SAFE_RENEGOTIATION, epriv);

  return 0;
}

static int
_gnutls_sr_recv_params (gnutls_session_t session,
                        const uint8_t * data, size_t _data_size)
{
  unsigned int len = data[0];
  ssize_t data_size = _data_size;
  sr_ext_st *priv;
  extension_priv_data_t epriv;
  int set = 0, ret;

  DECR_LEN (data_size, len + 1 /* count the first byte and payload */ );

  if (session->internals.priorities.sr == SR_DISABLED)
    {
      gnutls_assert ();
      return 0;
    }

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0 && session->security_parameters.entity == GNUTLS_SERVER)
    {
      set = 1;
    }
  else if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  if (set != 0)
    {
      priv = gnutls_calloc (1, sizeof (*priv));
      if (priv == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_MEMORY_ERROR;
        }
      epriv.ptr = priv;
    }
  else
    priv = epriv.ptr;

  /* It is not legal to receive this extension on a renegotiation and
   * not receive it on the initial negotiation.
   */
  if (session->internals.initial_negotiation_completed != 0 &&
      priv->connection_using_safe_renegotiation == 0)
    {
      gnutls_assert ();
      return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
    }

  if (len > sizeof (priv->ri_extension_data))
    {
      gnutls_assert ();
      return GNUTLS_E_SAFE_RENEGOTIATION_FAILED;
    }

  if (len > 0)
    memcpy (priv->ri_extension_data, &data[1], len);
  priv->ri_extension_data_len = len;

  /* "safe renegotiation received" means on *this* handshake; "connection using
   * safe renegotiation" means that the initial hello received on the connection
   * indicated safe renegotiation.
   */
  priv->safe_renegotiation_received = 1;
  priv->connection_using_safe_renegotiation = 1;

  if (set != 0)
    _gnutls_ext_set_session_data (session,
                                  GNUTLS_EXTENSION_SAFE_RENEGOTIATION, epriv);
  return 0;
}

static int
_gnutls_sr_send_params (gnutls_session_t session, gnutls_buffer_st* extdata)
{
  /* The format of this extension is a one-byte length of verify data followed
   * by the verify data itself. Note that the length byte does not include
   * itself; IOW, empty verify data is represented as a length of 0. That means
   * the minimum extension is one byte: 0x00.
   */
  sr_ext_st *priv;
  int ret, set = 0, len;
  extension_priv_data_t epriv;
  size_t init_length = extdata->length;

  if (session->internals.priorities.sr == SR_DISABLED)
    {
      gnutls_assert ();
      return 0;
    }

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0)
    {
      set = 1;
    }

  if (set != 0)
    {
      priv = gnutls_calloc (1, sizeof (*priv));
      if (priv == NULL)
        {
          gnutls_assert ();
          return GNUTLS_E_MEMORY_ERROR;
        }
      epriv.ptr = priv;

      _gnutls_ext_set_session_data (session,
                                    GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                    epriv);
    }
  else
    priv = epriv.ptr;

  /* Always offer the extension if we're a client */
  if (priv->connection_using_safe_renegotiation ||
      session->security_parameters.entity == GNUTLS_CLIENT)
    {
      len = priv->client_verify_data_len;
      if (session->security_parameters.entity == GNUTLS_SERVER)
        len += priv->server_verify_data_len;
      
      ret = _gnutls_buffer_append_prefix(extdata, 8, len);
      if (ret < 0)
        return gnutls_assert_val(ret);

      ret = _gnutls_buffer_append_data(extdata, priv->client_verify_data,
        priv->client_verify_data_len);
      if (ret < 0)
        return gnutls_assert_val(ret);

      if (session->security_parameters.entity == GNUTLS_SERVER)
        {
          ret = _gnutls_buffer_append_data(extdata, priv->server_verify_data,
            priv->server_verify_data_len);
          if (ret < 0)
            return gnutls_assert_val(ret);
        }
    }
  else
    return 0;

  return extdata->length - init_length;
}

static void
_gnutls_sr_deinit_data (extension_priv_data_t priv)
{
  gnutls_free (priv.ptr);
}

/**
 * gnutls_safe_renegotiation_status:
 * @session: is a #gnutls_session_t structure.
 *
 * Can be used to check whether safe renegotiation is being used
 * in the current session.
 *
 * Returns: 0 when safe renegotiation is not used and non (0) when
 *   safe renegotiation is used.
 *
 * Since: 2.10.0
 **/
int
gnutls_safe_renegotiation_status (gnutls_session_t session)
{
  int ret;
  sr_ext_st *priv;
  extension_priv_data_t epriv;

  ret = _gnutls_ext_get_session_data (session,
                                      GNUTLS_EXTENSION_SAFE_RENEGOTIATION,
                                      &epriv);
  if (ret < 0)
    {
      gnutls_assert ();
      return 0;
    }
  priv = epriv.ptr;

  return priv->connection_using_safe_renegotiation;
}
